Police are combing through a dam on a farm in Dereel, around 80km from Geelong, using an excavator in the search for Whitehead, 42, who was last seen in 2013.

The mother-of-five went missing on February 8, 2013, in nearby Bannockburn, where she lived.

She was seen leaving her home at 4.40pm that day and CCTV footage captured her visiting a supermarket in Bannockburn.

A witness reported seeing her get into the driver’s seat of a red 4WD in Bannockburn’s CBD.

The dam search is based on information Whitehead’s remains may be located in the area, police said.

Police, who described her disappearance as “extremely out of character” and “extremely concerning” have released an age progression image of Whitehead.

Whitehead is described as 170cm tall, with a medium build, brown eyes, and brown hair, and she was wearing black pants and a light-coloured shirt with a collar when she was last seen.

Detective Sergeant Steve Murphy, Moorabool Crime Investigation Unit, said Whitehead’s family are nearing 12 years without their loved one.

He reiterated calls for anyone with information to come forward.

“Lorrin’s family and friends have spent more than a decade not knowing what happened to Lorrin and we want to provide them with some answers,” Murphy said.

“We know there is someone out there who has information that can assist us in working out exactly what happened to Lorrin and provide closure to her loved ones and the tight-knit community of Bannockburn.

“Our team will continue to follow up every new piece of information we receive until Lorrin is found.”

“The unknown is the hardest part, and every day you are so missed, you are so missed,” the mother’s oldest daughter, Amelia, told 9News in 2015.

“I trust my instincts, there was nothing wrong the last time I spoke to her.”